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http:// www. navy.mil/navydata/fact_display.asp?cid=4100&tid=200&ct=4
"The Navy's ballistic missile submarines, often referred to as "boomers," serve as an undetectable launch platform for intercontinental missiles. They are designed specifically for stealth and the precise delivery of nuclear warheads.
Each of the 14 Ohio-class SSBNs can carry up to 20 submarine-launched ballistic missiles (SLBMs) with multiple, independently-targeted warheads. However, under the New Strategic Arms Reduction Treaty, each submarine will have four of its missile tubes permanently deactivated in the coming years. The SSBN's strategic weapon is the Trident II D5 missile, which provides increased range and accuracy over the now out-of-service Trident I C4 missile."